1. Field of the Invention
The present invention concerns an adjustment arrangement for a measuring head, in particular an adjustment arrangement for simplifying the calibration of a measurement probe supported by a measuring head.
2. Description of the Related Art
A measuring head is normally used to orient the measurement probe such that a measurement point can be taken, that is to say, determined. A normal measuring head can be rotated in two mutually perpendicular angles in such a manner that the tip of the measurement probe will travel along the outer surface of a sphere. A number of different orientations are normally used in a measurement program, and a calibration of the various positions in order to determine the diameter and offset of the probe is carried out, such that it will be possible to use the orientations with high precision.
Different types of measuring head are currently commercially available. One of these is the type known as “indexable”. The measuring head can in this case be set into a number of discrete index locations with, for example, a stem of 5° between the different steps. There are two principal variants of this type, manual and automatic. The angle of the measuring head is changed manually in the manual variant, normally by means of loosening a locking screw such that the setting of the measuring head can be changed. The same procedure occurs in principle in the automatic variant, but in this case with the aid of motors built into the measuring head.
Measuring heads are also available of a type known as “continuous”, in which the tip of the probe can adopt a freely chosen position on the hemisphere and the angles then are measured with the aid of angle sensors. The continuous measuring heads are automatic, i.e. they use motors to change the position. The use is, in principle, the same as that described above, i.e. the measuring heads are calibrated before use, and it is subsequently solely the reproducible precision of the measuring head itself that determines the precision.
One disadvantage of the types of measuring head described above, particularly the automatic designs with motors for turning to different angles, is that they are relatively expensive.
However, a method of using a manually indexable measuring head in an automatic manner has recently been introduced. This takes place in that the machine is used to unlock the locking screw and to carry out a change of angle. It is possible in this manner to use a manually indexable measuring head in an automatic process.
Also this latter method has, however, disadvantages such as, for example, the cost of a manually indexable measuring head is still relatively high. A second disadvantage is that the method still offers only a limited number of positions, the index steps, and a further disadvantage is that the precision depends totally on the reproducible precision of the measuring head.